Downhole tools such as frac plugs must both seal the wellbore during a well completion operation, such as fracking in the zone above the tool, and then subsequently permit fluid flow through the wellbore. Rubber and other elastomeric materials are commonly used as seals in settable downhole tools. While elastomeric materials function well as seals, they may interfere with completion operations, sometimes gumming up the mill head during milling the tool out, require tool retrieval, or otherwise delay or interfere with production.